Compound change gear transmissions are well known in the heavy duty truck field as they are employed to provide a greater number of gear ratio selections that are essential to the operation of heavy duty trucks particularly in mountainous terrain.
Such compound change gear transmissions generally feature a main section having a rotary mainshaft and a plurality of selectable gear ratios to which is added in auxiliary section having a rotary auxiliary shaft that is in substantial axial alignment with the mainshaft and provides an additional number of selectable gear ratios and which is selectively clutchable to the mainshaft through an auxiliary drive gear that is mounted near an end of the mainshaft adjacent an end of the auxiliary shaft. More particularly, for what is known in the trade as 2.times.2 compound transmissions, the auxiliary gear rotates about the mainshaft and is clutchable thereto by means of clutch assembly that is splined to the mainshaft. For 2-speed type compound transmissions the auxiliary gear is splined for rotation with the mainshaft and the clutch assembly is splined to the auxiliary shaft.
Vehicular compound change gear transmissions of the type herein concerned are disclosed for example in U.S. Pat. Nos. 4,944,197 and 5,000,060, the disclosures of which are incorporated herein by reference and both of which are assigned to the assignee of the present invention.
More particularly, the compound gear change transmission of the type herein concerned features an auxiliary drive gear that either rotates freely about the mainshaft or is secured to the mainshaft for rotation therewith and has a hub that extends coaxially through the inner race of a bearing assembly that provides rotational support for the mainshaft is provided with sufficient clearance to enable the mainshaft to float at least to the degree required to enable smooth engagement between the mainshaft and auxiliary shaft gears.
Whereas a portion of the auxiliary drive gear has heretofore been disposed between the bearing assembly and the mainshaft and has thus had its radial movement limited to the radial movement associated with the floating mainshaft, the present invention provides various combinations of spacers that enable the elimination of all radial contact between the auxiliary drive gear and the bearing assembly such that the clutchability of the auxiliary drive gear is advantageously enhanced due to the increased degree of radial movement established between the auxiliary drive gear and the mainshaft.